Re: [Patch v2 08/15] CIFS: SMBD: Support page offset in RDMA send

From: Tom Talpey
Date: Sat Jun 23 2018 - 22:11:44 EST


On 5/30/2018 3:48 PM, Long Li wrote:
From: Long Li <longli@xxxxxxxxxxxxx>

The RDMA send function needs to look at offset in the request pages, and
send data starting from there.

Signed-off-by: Long Li <longli@xxxxxxxxxxxxx>
---
fs/cifs/smbdirect.c | 27 +++++++++++++++++++--------
1 file changed, 19 insertions(+), 8 deletions(-)

diff --git a/fs/cifs/smbdirect.c b/fs/cifs/smbdirect.c
index c62f7c9..6141e3c 100644
--- a/fs/cifs/smbdirect.c
+++ b/fs/cifs/smbdirect.c
@@ -17,6 +17,7 @@
#include <linux/highmem.h>
#include "smbdirect.h"
#include "cifs_debug.h"
+#include "cifsproto.h"
static struct smbd_response *get_empty_queue_buffer(
struct smbd_connection *info);
@@ -2082,7 +2083,7 @@ int smbd_send(struct smbd_connection *info, struct smb_rqst *rqst)
struct kvec vec;
int nvecs;
int size;
- int buflen = 0, remaining_data_length;
+ unsigned int buflen = 0, remaining_data_length;
int start, i, j;
int max_iov_size =
info->max_send_size - sizeof(struct smbd_data_transfer);
@@ -2113,10 +2114,17 @@ int smbd_send(struct smbd_connection *info, struct smb_rqst *rqst)
buflen += iov[i].iov_len;
}
- /* add in the page array if there is one */
+ /*
+ * Add in the page array if there is one. The caller needs to set
+ * rq_tailsz to PAGE_SIZE when the buffer has multiple pages and
+ * ends at page boundary
+ */
if (rqst->rq_npages) {
- buflen += rqst->rq_pagesz * (rqst->rq_npages - 1);
- buflen += rqst->rq_tailsz;
+ if (rqst->rq_npages == 1)
+ buflen += rqst->rq_tailsz;
+ else
+ buflen += rqst->rq_pagesz * (rqst->rq_npages - 1) -
+ rqst->rq_offset + rqst->rq_tailsz;
}

This code is really confusing and redundant. It tests npages > 0,
then tests npages == 1, then does an else. Why not call the helper
like the following smbd_send()?

Tom.

if (buflen + sizeof(struct smbd_data_transfer) >
@@ -2213,8 +2221,9 @@ int smbd_send(struct smbd_connection *info, struct smb_rqst *rqst)
/* now sending pages if there are any */
for (i = 0; i < rqst->rq_npages; i++) {
- buflen = (i == rqst->rq_npages-1) ?
- rqst->rq_tailsz : rqst->rq_pagesz;
+ unsigned int offset;
+
+ rqst_page_get_length(rqst, i, &buflen, &offset);
nvecs = (buflen + max_iov_size - 1) / max_iov_size;
log_write(INFO, "sending pages buflen=%d nvecs=%d\n",
buflen, nvecs);
@@ -2225,9 +2234,11 @@ int smbd_send(struct smbd_connection *info, struct smb_rqst *rqst)
remaining_data_length -= size;
log_write(INFO, "sending pages i=%d offset=%d size=%d"
" remaining_data_length=%d\n",
- i, j*max_iov_size, size, remaining_data_length);
+ i, j*max_iov_size+offset, size,
+ remaining_data_length);
rc = smbd_post_send_page(
- info, rqst->rq_pages[i], j*max_iov_size,
+ info, rqst->rq_pages[i],
+ j*max_iov_size + offset,
size, remaining_data_length);
if (rc)
goto done;